Data security is imperative for a broad spectrum of applications, particularly in the commercial and government sectors. Cryptography is one of the most trusted and widely used approaches for securing data in transit and data at rest. By obfuscating the data through a reversible transformation, encryption provides a way to ensure the confidentiality of data when the security of communication links or data storage devices cannot be guaranteed. For example, the Internet Protocol Security (IPsec) protocol encrypts IP packets, allowing confidential data to be transmitted over public IP networks.
Commercial and government organizations typically store their data using various types of Redundant Array of Independent Disks (RAID) configurations in order to maximize data availability. By partitioning data fields into small data units and striping the data blocks across parallel disk drives, RAIDs allow data to be stored and accessed faster than if it were stored on a single drive. RAIDs also provide various levels of error correction that guard against the failure of an individual drive in the array. When a drive fails, most systems allow an operator to replace the drive without interrupting the operation of the system. Some RAID configurations allow the RAID control device to automatically reconstruct the contents of the drive from the available error correction information.
While magnetic disk drives such as RAIDs represent a high-performance and relatively inexpensive medium for data storage, it should also be noted that such magnetic disk drives have a limited operational life. As such, commercial and government organizations must periodically discard old and/or failed magnetic drives. The vast stockpile of discarded and/or failed magnetic drives represents a significant security risk and liability for commercial and government enterprises. Even with failed drives, while some component of the drive may have failed, a significant amount of data may still be recovered from the magnetic disk. Drives may be sent to a destruction facility that physically grinds the drives into small pieces, but this is an expensive process and requires a significant amount of physical security measures to be implemented for the transport of the failed drives to such a facility. Encryption represents a more secure and cost effective option for securing stored data. By encrypting each data block prior writing it to disk and decrypting each data block after reading it from disk, stored data is obfuscated and protected from physical theft of the drive before or after drive failure. Cryptography may be employed in data communication and storage applications in a variety of other ways. The prior two examples simply highlight the tangible benefits. Other applications include securing digital voice, video, and image data.
A symmetric key block cipher is the most common type of cryptography employed for data confidentiality. Given a fixed-size block of input data (or plaintext) and a key, a block cipher produces a fixed-size block of encrypted output data (or ciphertext) using an unvarying transformation. A block cipher that uses the same key to encrypt and decrypt data is called a symmetric key block cipher. The Advanced Encryption Standard (AES) specified by the National Institute of Standards and Technology (NIST) is the Rijndael block cipher operating on data blocks of size 128 bits and using keys of size 128 bits, 192 bits, or 256 bits. Each transformation step in the Rijndael block cipher is referred to as a round. AES specifies the number of rounds based on the key size: 128 bit keys use 10 rounds, 192 bit keys use 12 rounds, and 256 bit keys use 14 rounds.
Despite advances in cryptographic algorithms, encryption and decryption remain computationally intensive tasks. For software applications running on general purpose processors (GPPs), adding a software implementation of encryption and decryption consumes a significant amount of processing resources, thus reducing the achievable performance of the application. One advantage of block ciphers such as AES block ciphers is their amenability to pipelined hardware implementation. In the case of AES, the inputs and processing of one round need not depend on the results of a subsequent round; i.e. there are no inherent feedback loops in the execution of the algorithm. A fully pipelined hardware implementation for AES could instantiate a series of 14 round circuits where each round circuit implements one round of the AES block cipher. An example of such an implementation is shown in FIG. 12. Depending on the key size in use, a supporting control circuit intercepts the state data at the appropriate round to be output as ciphertext. For a key size of 128 bits, the output of round 10 is used as the ciphertext. For a key size of 192 bits, the output of round 12 is used as the ciphertext. For a key size of 256 bits, the output of round 14 is used as the ciphertext. Regardless of key size, the pipelined block cipher circuit of FIG. 12 can be made to accept one block of data per clock cycle and only a single pass through the pipeline is needed to encrypt data. The resulting throughput for the circuit of FIG. 12 is the achievable clock frequency multiplied by the block size. A conservative estimate in current technology is a clock frequency of 200 MHz, resulting in a throughput of 25.6 Gbps (billion bits per second).
However, in many instances, the throughput needs of an encryption/decryption system will need to be balanced with the desired amounts of power consumption within the system. It should be noted that at higher clock frequencies and larger numbers of pipeline rounds, the power consumed by the block cipher when encrypting/decrypting data will increase. Therefore, the inventors herein believe that a need exists in the art for a block cipher design that is scalable to balance throughput goals against power consumption goals.
Toward this end, the inventors disclose as an embodiment of the invention a scalable block cipher circuit, wherein the scalable block cipher circuit is scalable to balance throughput with power consumption as desired by a practitioner of this embodiment of the invention. The scalable block circuit can be deployed on an integrated circuit, preferably as a hardware logic circuit on the integrated circuit. Optionally, this hardware logic circuit can be realized using reconfigurable logic. However, it should also be noted that this hardware logic circuit can be realized using non-reconfigurable logic (e.g., deployed as an application specific integrated circuit (ASIC)).
As used herein, “hardware logic circuit” refers to a logic circuit in which the organization of the logic is designed to specifically perform an algorithm and/or application of interest by means other than through the execution of software. For example, a GPP would not fall under the category of a hardware logic circuit because the instructions executed by the GPP to carry out an algorithm or application of interest are software instructions. As used herein, the term “GPP” refers to a hardware device that fetches instructions and executes those instructions (for example, an Intel Xeon processor or an AMD Opteron processor). Examples of hardware logic circuits include ASICs and reconfigurable logic circuits. The term “reconfigurable logic” refers to any logic technology whose form and function can be significantly altered (i.e., reconfigured) in the field post-manufacture. This is to be contrasted with a GPP, whose function can change post-manufacture, but whose form is fixed at manufacture. This can also be contrasted with those hardware logic circuits whose logic is not reconfigurable, in which case both the form and the function are fixed at manufacture (e.g., an ASIC, as mentioned above). An example of a reconfigurable logic circuit is a field programmable gate array (FPGA). Furthermore, the term “firmware” refers to data processing functionality that is deployed in a hardware logic circuit such as an ASIC or FPGA. The term “software” will refer to data processing functionality that is deployed on a GPP.
As another embodiment, the inventors disclose a block cipher circuit comprising a plurality of pipelined round circuits, wherein the block cipher circuit is configured to perform encryption and decryption utilizing the same order of round circuits within the pipeline regardless of whether encryption or decryption is being performed. Furthermore, such a block cipher circuit can employ multiplexers within a plurality of the round circuits to adjust the order of stages within each round circuit to accommodate both encryption and decryption operations. Further still, such a block circuit can employ on-the-fly key expansion and inverse expansion.
While the use of a strong block cipher, a large key size, and a clever encryption mode significantly reduces the probability of a successful attack on ciphertext, it should also be noted that key management is of equal importance in protecting the security of encrypted data. Key management represents one of the most challenging aspects of data security. As used herein, “key management” refers to the process of selecting, generating, authenticating, distributing, updating, and storing the keys used by a block cipher for encrypting/decrypting data. As used herein, “key management function” refers to a specific key management task (e.g., key generation, key distribution, etc.).
To address a perceived need in the art for improved key management security, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption, wherein the integrated circuit is also configured to perform a plurality of different types of key management functions (e.g., key management functions such as key selection, key generation, key authentication, key distribution, and key storage). The inventors also note that a challenge to integrating multiple type of key management functions into a single integrated circuit is the constraint as to the amount of space available on the integrated circuit. Thus, an efficient design for integrated key management is needed such as the inventive embodiments disclosed herein.
Further still, to increase the flexibility of encryption/decryption, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption wherein an encryption mode wrapper circuit is included on the integrated circuit for selectively performing additional operations on data going to and/or coming from the block cipher circuit to thereby define a desired encryption mode for the encryption operation. Preferably, the encryption mode wrapper circuit is realized as a hardware logic circuit on the integrated circuit.
Further still, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption wherein a data routing and control circuit is included on the integrated circuit for performing various data routing and control functions among the various circuits that are also included on the integrated circuit. Preferably, the data routing and control circuit is realized as a hardware logic circuit on the integrated circuit.
Further still, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption wherein volatile memory is included on the integrated circuit for temporarily storing any plaintext data that is needed by the integrated circuit during its operation, to thereby prevent exposure of plaintext outside the integrated circuit.
Further still, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption wherein volatile memory is included on the integrated circuit for temporarily storing any keys used by the block cipher circuit to encrypt/decrypt data, to thereby prevent exposure of the actual keys used by the block cipher for encryption/decryption outside the integrated circuit.
Further still, the inventors disclose as an embodiment of the invention an integrated circuit configured to perform encryption/decryption and a plurality of different types of key management functions, wherein the integrated circuit comprises a scalable block cipher circuit, an encryption mode wrapper circuit, a data routing and control circuit, and volatile memory for storing data and keys. Preferably, these circuits are realized as hardware logic circuits on the integrated circuit. The integrated circuit can also include a Direct Memory Access (DMA) engine circuit for reading data and commands into and writing data and commands out of the integrated circuit. The DMA engine circuit may also preferably be realized as a hardware logic circuit.
These and other features, advantages, and embodiments of the present invention will be apparent to those having ordinary skill in the art upon review of the following drawings and detailed description.